@LorenzoAncora >guarantee compatibility with older web browsers
Proprietary JS site do not support older browsers - those are primarily designed to run only on chrome and sometimes those run on firefox too.
If the browser doesn't support the used HTML5 features, chances are it won't support the execution of the JavaScript framework used either.
>the verification of data integrity and correctness happens server-side too, not only client-side.
It is a waste of electricity to check twice when you only need to check once.
Processing and altering collected data is up to the server.
If the task is processing and altering information for the user, then the user should do such processing on their own computer with free software without involving a server.
JavaScript exists because it was too easy to think that adding cancer in the form of scripting would make things nicer.